Surface modification of CrFeCoNiMo high entropy alloy induced by high-current pulsed electron beam

The surface of non-equiatomic CrFeCoNiMo high entropy alloy (HEA) was irradiated by high-current pulsed electron beam (HCPEB). Microstructure, mechanical properties and corrosion resistance of the CrFeCoNiMo HEA before and after HCPEB irradiation were studied systematically. The results of XRD analysis indicated that the surface of the irradiated samples exhibited preferential orientation on (1 1 1) and (2 0 0). Microstructure observations revealed that a compact remelted layer was formed on the surface of the alloy after HCPEB irradiation, the thickness of the remelted layer rose as the increase of pulse numbers. Besides, numerous nano sigma particles, nanocrystallites with an average size about 109 nm and abundant deformed structures also appeared in the remelted layer. The mechanical properties of CrFeCoNiMo alloy were significantly enhanced after HCPEB treatment, which was mainly ascribed to intense plastic deformation via stress, sub-grain strengthening along with precipitation hardening. Electrochemical results demonstrated that all the irradiated specimens had a positive potential and a lower current density in 3.5 wt% NaCl solution compared with the untreated sample. The homogenized surface and the efficient eliminating of the local concentration of Cr element jointly contributed to the improvement of corrosion resistance.